## Diff of /inst/unvech.m[b87ccd] .. [20a2cc] Maximize Restore

### Switch to side-by-side view

```--- a/inst/unvech.m
+++ b/inst/unvech.m
@@ -15,7 +15,7 @@
##
## You should have received a copy of the GNU General Public License
## along with this program; If not, see <http://www.gnu.org/licenses/>.
-
+
## -*- texinfo -*-
## @deftypefn {Function File} {@var{m} =} unvech (@var{v}, @var{scale})
## Performs the reverse of @code{vech} on the vector @var{v}.
@@ -27,31 +27,44 @@
## that 1 and -1 can be used for symmetric and antisymmetric matrix respectively.
## @var{scale} must be a scalar and defaults to 1.
##
-## @seealso{vech, ind2sub, sub2ind_tril}
+## @seealso{vech, ind2sub}
## @end deftypefn
-
+
function M = unvech (v, scale = 1)
-
+
if ( nargin < 1 || nargin > 2 )
print_usage;
elseif ( !ismatrix (v) && any (size (v) != 1) )
-    error ("V must be a row orcolumn matrix")
+    error ("V must be a row or column matrix")
elseif ( !isnumeric (scale) || !isscalar (scale) )
error ("SCALE must be a scalar")
endif
-
+
N      = length (v);
dim    = (sqrt ( 1 + 8*N ) - 1)/2;
[r, c] = ind2sub_tril (dim, 1:N);
M      = accumarray ([r; c].', v);
M     += scale * tril (M, -1).';
-
+
endfunction

+function [r c] = ind2sub_tril(N,idx)
+
+  %% Horrible lengthly check
+  if nargin < 2 ||( !isnumeric (N) && all(size(N)==1) )|| ...
+    !( ismatrix (idx) && any (size (idx)==1) )
+    print_usage;
+  endif
+
+  endofrow = 0.5*(1:N) .* (2*N:-1:N + 1);
+  c = lookup(endofrow, idx-1)+1;
+
+  r = N - endofrow(c) + idx ;
+
+end
+
%!assert(unvech([1;0;0;1;0;1]), full(eye(3,3)) );
-
-#%!error <does not generate a square matrix> unvech([1;0;0;1;0;1;1]);
-
+
%!test %symmetric
%! dim = 10;
%! A = tril( floor ( 5*(2*rand(dim)-1) ) );
@@ -59,7 +72,7 @@
%! M = vech(A);
%! M = unvech(M, 1);
%! assert (A, M);
-
+
%!test %antisymmetric
%! dim = 10;
%! A = tril( floor ( 5*(2*rand(dim)-1) ) );
@@ -67,3 +80,4 @@
%! M = vech(A);
%! M = unvech(M, -1);
%! assert (A, M);
+
```